U.S. patent number 6,139,320 [Application Number 08/700,543] was granted by the patent office on 2000-10-31 for apparatus, method and expedient materials for ultrasonic preparation of human and animal hard or soft tissues and of dental or bone replacement materials as well as object obtained thereby.
Invention is credited to Rainer Hahn.
United States Patent |
6,139,320 |
Hahn |
October 31, 2000 |
Apparatus, method and expedient materials for ultrasonic
preparation of human and animal hard or soft tissues and of dental
or bone replacement materials as well as object obtained
thereby
Abstract
For ultrasonic preparation of hard or soft tissues or of tissue
replacement material a apparatus is proposed comprising a hand
piece (10), which includes an ultrasonic vibration generator (16),
an ultrasonics deflecting head (28) as well as a tool (36) carried
by the output member of the deflecting head. An abrasive treatment
medium (48) is supplied to the working region defined between the
tool (36) and the material (66) to be prepared. Thus even in
places, which are difficult to access, cavities can be produced in
dental or bone tissue in a gentle and precise manner.
Inventors: |
Hahn; Rainer (D-72074 Tubingen,
DE) |
Family
ID: |
6511297 |
Appl.
No.: |
08/700,543 |
Filed: |
August 28, 1996 |
PCT
Filed: |
February 27, 1995 |
PCT No.: |
PCT/EP95/00710 |
371
Date: |
August 28, 1996 |
102(e)
Date: |
August 28, 1996 |
PCT
Pub. No.: |
WO95/22938 |
PCT
Pub. Date: |
August 31, 1995 |
Foreign Application Priority Data
|
|
|
|
|
Feb 27, 1994 [DE] |
|
|
4406323 |
|
Current U.S.
Class: |
433/119; 433/86;
433/88 |
Current CPC
Class: |
A61C
1/07 (20130101); A61C 17/20 (20130101); B06B
3/00 (20130101); B29C 65/08 (20130101); B29C
66/80 (20130101); B29C 66/861 (20130101); G10K
11/02 (20130101); A61C 5/40 (20170201); A61B
2017/320069 (20170801); B29C 66/9516 (20130101); B29C
66/9517 (20130101); B29C 66/81241 (20130101); B29C
66/7392 (20130101); A61B 2017/320082 (20170801); A61B
2017/32007 (20170801); A61B 2017/320089 (20170801); A61C
3/025 (20130101) |
Current International
Class: |
A61C
1/00 (20060101); A61C 1/07 (20060101); A61C
17/20 (20060101); A61C 5/02 (20060101); B06B
3/00 (20060101); A61C 17/16 (20060101); A61B
17/32 (20060101); B29C 65/08 (20060101); G10K
11/00 (20060101); G10K 11/02 (20060101); A61C
3/025 (20060101); A61C 3/02 (20060101); A61C
001/07 (); A61C 003/03 (); A61C 003/08 () |
Field of
Search: |
;433/119,86,88 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lucchesi; Nicholas D.
Claims
What is claimed is:
1. An apparatus for ultrasonic preparation of at least one of human
and animal hard and soft tissue and dental and bone replacement
materials, comprising:
an ultrasonic vibration generator (16),
a tool (36, 80, 86, 96, 98, 106, 120, 134, 140, 148, 156, 176)
driven thereby, and
a sound deflecting head (28) arranged between said vibration
generator (16) and said tool and having a driven input (33, 162a)
that is movable in a direction parallel to a longitudinal axis of
said vibration generator (16) and a driving output (34, 162d) that
is movable along an axis cooperating with said longitudinal axis of
said vibration generator (16) to define an angle different from
zero degrees,
in which said tool is connected to said driving output (34, 162d)
of said deflecting head (28).
2. The apparatus according to claim 1, in which said tool vibrates
in a direction parallel to a longitudinal axis of said tool.
3. The apparatus according to claim 2, in which said deflecting
head (28) comprises a vibrating member (162) having a resonant
frequency coinciding with an operating frequency of said vibration
generator (16), vibration induced in said vibrating member (162)
has a plurality of circumferentially spaced maxima of vibration,
and said vibrating member (162) has a first ring portion (162a)
associated with a first maximum of vibration that is coupled to
said vibration generator (16) and a second ring portion (162d)
associated with a different maximum of vibration that is coupled to
said tool.
4. The apparatus according to claim 3, in which said vibrating
member (152) is selected from the group consisting of a ring, a
sleeve, and a hollow sphere.
5. The apparatus according to claim 1, in which said deflecting
head comprises a deflector housing (30) having a deflector channel
(32) containing a volume of at least one liquid or gas.
6. The apparatus according to claim 5, in which said deflector
channel (32) has ends enclosed in a fluid tight manner by at least
one of a diaphragm (33, 34) and a movable plunger.
7. The apparatus according to claim 6, in which said at least one
diaphragm (33, 34) and plunger is oriented perpendicular to said
longitudinal axis of said vibration generator (16) and a
longitudinal axis of said tool (36), respectively.
8. The apparatus according to claim 7, in which said diaphragm (33,
34) has a thickness that decreases from a periphery of said
diaphragm that is connected to said deflector housing (30) towards
a center of said diaphragm.
9. The apparatus according to claim 8, in which said diaphragm (33,
34) is made of at least one metal and metal alloy.
10. The apparatus according to claim 5, in which said volume of
liquid (35) contained in said deflector channel (32) has low
viscosity at least when exposed to ultrasonics.
11. The apparatus according to claim 10, in which said volume of
liquid (35) is selected from the group consisting of quick silver,
water, alcohol, alcohol-water mixtures, silicone oils, and liquid
phase nickel alloys.
12. The apparatus according to claim 1, in which an angle between
said longitudinal axis of said vibration generator (16) and a
longitudinal axis of said tool is between approximately 60 degrees
and 120 degrees.
13. The apparatus according to claim 12, in which said angle
between said longitudinal axis of a vibration generator (16) and
said longitudinal axis of said tool is 90 degrees.
14. The apparatus according to claim 1, in which said vibration
generator (16), said deflecting head (28), and said tool comprise
an overall system that oscillates at resonance frequency.
15. The apparatus according to claim 1, in which said tool
comprises a negative model of a shaped filling member (88, 92, 176)
that is made from tissue replacement material, and said tool and
said deflecting head (28) are formed such that said tool can be
sunk while oscillating at least partially into material to be
treated.
16. The apparatus according to claim 15, further comprising a set
of different tools designed for different sizes of teeth and
different minimum preparation depths.
17. The apparatus according to claim 16, in which said set of
different tools are specific for replacement material used and
represent negative models corresponding to different shaped filling
members.
18. The apparatus according to claim 17, further comprising a set
of shaped filling members that are provided in same shapes and size
gradations as said tools.
19. The apparatus according to claim 18, in which said shaped
filling members are selected from a group consisting of ceramic
material, polymer composite material, and metal, and have surfaces
that are at least partially coated with fixing materials.
20. The apparatus according to claim 19, in which said surfaces are
positively connected by means of at least one of force and
geometry.
21. The apparatus according to claim 15, further comprising a
shaped filling member to be inserted in a tissue cavity in which
said tool and said shaped filling member to be inserted into a
tissue cavity are both formed by a shaped filling member (156, 176)
comprised of a biocompatible hard material.
22. The apparatus according to claim 21, in which said shaped
filling member (156, 176) is comprised of a material selected from
oxide-type ceramic material, non-oxide type ceramic material, and
metallic material.
23. The apparatus according to claim 21, in which said shaped
filling member (156, 176) comprises a mounting portion (178)
connectable to said driving output member (34, 162b) of said
deflecting head (28) and connected to a portion (176) of said
shaped filling member to be inserted into a tissue cavity by means
of a rated break point (180).
24. The apparatus according to claim 23, in which said mounting
portion (178) is connected to said inserted portion of said shaped
filling member by at least one connection selected from screwing,
wedging, and soldering.
25. A method for ultrasonic preparation of at least one of dental
and bone replacement materials comprising the steps of obtaining
and using a tool according to claim 15.
26. A method for ultrasonic preparation of at least one of human
and animal, hard and soft tissue, comprising the steps of obtaining
and using a tool according to claim 15.
27. The apparatus according to claim 1, in which said tool
comprises a work portion (144) of a material that heats when
exposed to ultrasonics.
28. The apparatus according to claim 27, in which said work portion
(144) is internally frictionally heated.
29. The apparatus according to claim 28, which said work portion
(144) comprises a plurality of different material layers.
30. The apparatus according to claim 1, comprising at least one
means (46, 50, 52, 164, 166, 168) supplying abrasive treatment
medium (48, 170) to said tool.
31. The apparatus according to claim 30, in which said abrasive
treatment medium (48, 170) comprises small abrasive sealing
particles (60) having an average diameter smaller than
approximately 5 .mu.m.
32. The apparatus according to claim 31, in which said average
diameter of said abrasive sealing particles (60) is approximately 1
.mu.m.
33. The apparatus according to claim 31, in which said abrasive
sealing particles comprise sealing particles (60) selected from the
group consisting of sealing particles of oxide-type, silicate-type,
carbide-type, nitride-type, and polymer-containing materials.
34. The appartus according to claim 31, in which said abrasive
sealing particles have surfaces that are apt to establish an at
least partly chemical compound with at least one of silanes and
polymers.
35. The apparatus according to claim 31, in which said abrasive
sealing particles are apt to be at least partly integrated into a
gel when exposed to jellying joint filling material at least partly
containing an acid.
36. The apparatus according to claim 31, in which one unit volume
of said abrasive sealing particles is used with two to twenty
volumes of abrasive particles.
37. The apparatus according to claim 36, in which one unit volume
of said abrasive sealing particles is used with ten unit volumes of
abrasive particles.
38. apparatus according to claim 31, in which said abrasive
treatment medium includes abrasive particles (56) having a diameter
that approximately corresponds to an overall stroke of said
ultrasonic vibration tool.
39. The apparatus according to claim 38, in which one unit volume
of abrasive particles is used with three to thirty unit volumes of
liquid.
40. The apparatus according to claim 39, in which one unit volume
of abrasive particles is used with five to twenty unit volumes of
liquid.
41. The apparatus according to claim 40, in which one unit volume
of abrasive particles is used with ten unit volumes of liquid.
42. The apparatus according to claim 31, in which said abrasive
sealing particles have at least one of a hydrophilic surface and a
hydrophilic surface coating.
43. The apparatus according to claim 30, in which said abrasive
treatment medium (130) comprises at least one gel.
44. The apparatus according to claim 43, in which said abrasive
treatment medium (130) has modified viscosity.
45. The apparatus according to claim 44, in which said modified
viscosity is realized by addition of aerosil and a gelling base
substance.
46. The apparatus according to claim 43, in which said abrasive
treatment medium is at least partly transferred into a liquid state
when exposed to ultrasonics.
47. The apparatus according to claim 43, in which a base component
of said abrasive treatment medium (130) is selected from at least
one of glycerin gel, a one to ten percent chloral-hexidine gel and
gelatin.
48. The apparatus according to claim 30, further comprising means
for supplying treatment liquid (48) to an exterior surface of said
tool.
49. A method of ultrasonic preparation of at least one of dental
and bone replacement materials comprising the steps of obtaining
and using an abrasive treatment apparatus according to claim
30.
50. A method for ultrasonic preparation of at least one of human
and animal, hard and soft tissue, dental and bone replacement
materials comprising the steps of obtaining and using an abrasive
treatment apparatus according to claim 30.
51. The apparatus according to claim 1, in which said tool at least
partially comprises a hollow member and is connected to means for
supplying abrasive treatment medium (164, 166, 168).
52. The apparatus according to claim 1, in which said tool (96)
comprises at least one convex vibrating head.
53. The apparatus according to claim 1, in which said tool has a
curved transversal cross-section.
54. The apparatus according to claim 1, in which said tool
comprises at least one of a flute-shaped work portion (124) and a
shovel-shaped work portion (124).
55. The apparatus according to claim 1, in which said tool has a
free end-face (100, 108) having a portion inclined with respect to
a longitudinal axis of said tool.
56. The apparatus according to claim 55, in which said free
end-face (108) of said tool (106) comprises a portion extending
perpendicularly to said longitudinal axis of said tool.
57. The apparatus according to claim 1, in which said tool has a
free end-face (100, 108) having a portion curved in the sense of a
flute.
58. The apparatus according to claim 1, in which said tool (134)
comprises a shaft and a transversal work portion (138) connected to
a free end of said shaft.
59. The apparatus according to claim 1, in which said tool (148)
comprises a chisel tip (154).
60. The apparatus according to claim 1, in which said tool has a
geometry corresponding to a geometry of a dental root channel
(158).
61. The apparatus according to claim 1, in which said tool has an
end portion that vibrates in a direction transversal to a
longitudinal axis of said tool.
62. A method for ultrasonic preparation of at least one of human
and animal, hard and soft tissue, dental and bone replacement
materials comprising the steps of obtaining an apparatus according
to claim 1 and using said apparatus in a dental procedure.
63. A method for treatment of soft tissue comprising the steps of
obtaining and using an apparatus according to claim 1.
64. A method for ultrasonic preparation of at least one of dental
and bone replacement materials comprising the steps of obtaining
and using an apparatus according to claim 1.
65. A method of forming a cavity in a tooth comprising the steps of
obtaining and using an apparatus according to claim 1 to form said
cavity.
Description
The present invention relates to an apparatus, a method and
expedient materials for ultrasonic preparation of human and animal
hard or soft tissues, particularly dental and bone materials, and
of artificial replacement materials as they are used for the
reconstruction of teeth or bones. The invention further relates to
objects obtained thereby.
Subtractive treatment of natural hard tissues, as e.g. dental
enamel, dental bone, dental cement and bones as well as of tooth or
bone replacement materials is the basis of almost any dental or
surgical intervention. Up to date the treatment of the said hard
tissues is carried out in every day work using rotary diamond or
hard metal tools or by use of sharp, e.g. chisel shaped manual
tools.
The use of such work tools results in pronounced vibrations,
production of unpleasant noises and induction of partly
considerable pains. There is the danger of excessive heating of the
vital tissues treated which may result in irreversible damages of
the organic components and adjacent organs, e.g. tooth pulp. In
addition it is impossible to selectively cut off material, e.g.
dental hard material, e.g. cariously degenerated dental hard
substances while saving adjacent healthy tissue. In the cutting
action of the tool formation of craters and fractures in the
brittle inorganic components of the tissue or the tissue is not
rare, e.g. also including possible chipping off of the dental
enamel jacket from the tooth bone during treatment of the enamel
using rotary diamond tools. In addition the minimum ratio between
cross section and length of the tools required for obtaining the
minimum stiffness necessary for a particular application impedes
the handling of the tools in regions, which are difficult to reach,
e.g. in thin elongates cavities, endodontic cavities and surface
portions extending along the tooth roots or therebetween. Last but
not least there is a high risk of injuring adjacent soft tissues by
rotary cutting tools by inadvertant sliding off, e.g. of manually
operated tools.
The geometry of the cavity obtained is the result of the geometric
form of the e.g. rotary tool as well as of the relative moment
between the tool and the workpiece; preparation of standard
geometric shapes is not possible.
Preparation of cavities specific for a particular indication is
carried out in accordance with predetermined basic rules (experts'
knowledge), which, however, due to the individually produced shapes
of the cavities cannot be used as "informations" for producing e.g.
tooth or bone restoring parts. Thus making reconstructions requires
a precise modelling of all the treated surfaces; smaller errors in
the imaging cannot be corrected by integration of the shape of
adjacent precisely modelled surface portions using the knowledge of
the expert.
The preparation of vital hard tissues using laser energy will
result in thermal damages as well as mechanical damages caused by
thermal shocks of the treated hard substances and adjacent tissue,
respectively, and such preparation is laborious and not economic as
compared to conventional treatment methods.
In addition the preparation of defined cavities is difficult due to
the uncontrollable cutting action in the depth coordinate as well
as by the non-tactile free handling of the tools. Futhermore there
is a danger of injuring the soft tissues by direct radiation and
reflection effects, respectively.
Preparation of dental hard tissues using fine alumina grain jet
installations is limited to a narrow range of applications and is
expensive due to the machining method, due to the hardly
controllable handling and due to the fact that a rubber dam must be
used. In addition there is a high risk of damaging the lungs of the
patient and of the medical staff due to the formation of dust,
which cannot be avoided.
The preparation of dental and bone tissues using oscillating tools
has already been described decades ago.
U.S. Pat. No. 2,874,470 (high frequency dental tool, 1959)
discloses the preparation of dental hard tissues using
magnetostrictive oscillation tools and abrasive liquids.
DE 11 00 424 discloses an amplitude transformer of an ultrasonic
drilling device for the treatment of teeth, which transformer is
split in a nodal plane of the vibration, which fact facilitates the
use of different machining tools.
Electromechanic and magnetostrictive (of the lamella type)
transducers for use in the treatment of teeth with oscillating
tools and using abrasive liquids are disclosed in U.S. Pat. No.
3,075,288.
Modern ultrasonic treatment tools, which have originated from this
state of prior art, comprise e.g. a piezoelectric vibration
generator, wherein end mass members of rotational symmetry are
coaxially fixed to the two end faces of the piezoelectric quartz
for amplifying the vibration by tuning the total system to
resonance frequency. In view of amplifying the amplitude end mass
members (sonotrodes) of rotational symmetry coaxially fixed to one
end of the generator are also useful, which also tuned into
resonance oscillation with the vibration generating system, the
cross section of which preferably progressively diminishes with
increasing distance from the piezoelectric quartz. A further end
mass member tuned to resonance frequency and representing a work
tool can be coaxially connected to the end face of the
sonotrode.
The entire system is in a state of harmonic longitudinal vibrations
along its longitudinal axis, the largest amplitudes being obtained
at that one of the end faces of the vibration amplifyer being
remote from the piezoelectric quartz and the system showing at
least one nodal plane being perpendicular to the longitudinal
system axis (=longitudinal axis of the vibration generator) and
extending through the center of the piezoelectric quartz.
Operation of the above tooth treatment tools in the ultrasonic
frequency region (about 18 kHz to 30 kHz) due to the physical
relations between the resonance frequency and the wave length
results in sufficient operating amplitudes of the preferably
metallic tool, around which a liquid is made to flow, and thus
causes cavitation effects causing machining of material,
particularly for removal of dental tartar. On the other hand the
wave length of the ultrasonic treatment tool operated in resonance
determines the structural dimension of the tool in the direction of
the longitudinal axis of the system and thus is not favourable for
using the tool in regions, which are difficult to acces.
Particularly treatment of lateral teeth can hardly be carried out
using prior art ultrasonic treatment tools because of the
physiologically limited mouth opening of about 40 to 50 mm.
In view of finding a solution to this problem the firm Cavitron
Ultrasonics in 1956 (U.S. Pat. No. 492,924) has described tools for
ultrasonic treatment of dental hard substances, which are
characterized by an eccentric distribution of the mass with respect
to the longitudinal axis of the system. Such tool are also
disclosed in DE 1 258 017, U.S. Pat. No. 2,990,616 and a scientific
paper by H. H. Postle published in J.Prosth.Dent.Vol.8, 1958, pages
153-160. Vibrational excitation of the tools, which have an
eccentric distribution of the mass, along the longitudinal axis of
the system results in the induction of transversal, particularly
ellipsoidal spacial vibrations of the treatment tool, so that there
is a component of the amplitude in each of the spacial directions.
However, the component of this amplitude along the direction of
preparation, which generally is perpendicular to the longitudinal
axis of the system (axis of the handpiece) is not sufficient for
producing cavities in teeth. The spacial vibrations also prevent
the formation of a continuous film of liquid between the tool and
the surface to be treated, which, however, is a prerequisite for
transfer of energy and machining of material, e.g. by cavitation
effects.
Furthermore, the uncontrollable, partly high amplitudes in the
various spacial directions cause mechanical damaging of the partly
brittle dental hard tissues (H. Sprange and G. Haim, ZWR Vol. 22
1969, pages 1028-1031). In addition removal of dental plaque by
such ultrasonic tools, which even today are still in use without
substantial modfications, results in significant roughening of the
treated tooth surfaces, which favours the formation of new plaque.
Last but no least the high amplitude bears the risk of thermal
damaging of hard and soft tissues.
The use of e.g. dental ultrasonic tools under continous cooling by
water is thus limited to the removal of supragingival dental
tartar. Up-to-date an application for preparing defined cavities,
for cleaning subgingival tooth surfaces, particularly those located
in pockets of the gingiva, for desirable cutting treatment of
endodontic cavities as well as for
treatment of dental and bone replacement materials is not possible
up-to-date.
Ultrasonics driven rotating tools using conventional cutting work
tools (diamond tools with bound grains or cutting hard metal tools)
are disclosed in U.S. Pat. No. 4,281,987, U.S. Pat. No. 4,289,149
as well as in a review paper by L. Balamuth, IEE 1963, pages
96-101. The machining mechanisms do not differ from conventional
rotary (air driven or motor driven) tools, the ultrasonic drive
being comparatively uneconomic.
AT 290 005 discloses a device for reproducibly machining teeth
using a "stationary" sleeve, which seems to be under the influence
of an "ultrasonic field". The "ultrasonic field" is not described
in more detail, although the graphical representation joined
represents the handling of the sleeve in the region of lateral
teeth.
Using the known ultrasonic treatment devices known up-to-date due
to the above mentioned physical principles it is not possible to
create in such a sleeve longitudinal work amplitudes being parallel
to the longitudinal axis of the tooth which are effective in this
sense of chipping material, particularly in the region of lateral
teeth. In such an application lateral and spacial vibrations would
result in a superposition of the vibration geometry and the
standard tool geometry, thus resulting in massive imaging errors in
the sinking in of the sleeve. A reconstruction using standard
crowns, which have been prefabricated in analogy to the shape of
the sleeve, is impossible, when there are spacial vibrations of the
treatment tool or the sleeve, since the geometry of the vibration
will result in geometric discrepancies between the treated surfaces
of the tooth stump and the interior surfaces of the
restoration.
On the other hand the use of standard tools as the sleeve mentioned
above or the tool disclosed in U.S. Pat. No. 2,874,470 for
preparing the total cavity of an inlay does little to save the
substance of a tooth, since teeth have individual geometries and
varying individual dimensions. Furthermore there is no safety e.g.
as to complete removal of sick portions of the tissue. Last but not
least there is the danger of inadvertant opening of adjacent, e.g.
endodontic cavities.
The object of the present invention is thus to provide an
ultrasonic treatment apparatus, wherein at the tool work amplitudes
are obtained which are effective in view of maching material, which
has a considerable shorter length than prior art ultrasonic
treatment instruments and can be handled in an ergonomically
favourable way like a prior art angled hand piece, thus allowing
for economic use of such a tool in regions, which are difficult to
access, e.g. in the intraoral treatment of hard tissue.
This object is solved by an apparatus in accordance with claim
1.
This apparatus has at least one deflecting head arranged between a
vibration generator and a treatment tool, the deflecting head being
driven for oscillation in a direction being parallel to the
longitudinal axis of the vibration generator and providing a
driving motion in the longitudinal direction of the treatment tool,
the longitudinal axis of the vibration generator and the
longitudinal axis of the treatment tool including an angle being
different from 0.degree..
Such deflecting heads can even be produced with substantially
smaller height than the vibration generating system itself, which
fact further facilitates handling of the treatment tool.
The geometric shape of the deflecting head modifying the direction
of the ultrasonic oscillation is formed specific to the particular
application. If it is a deflecting head comprising a vibrating
member showing a plurality of maxima of the vibration, these maxima
corresponding to the driven part and the driving part of the
deflecting head, the geometric shape together with the material(s)
determines its eigenfrequency as well as the form of the vibration
induced in the direction of the treatment tool.
Materials, which are particularly suited for providing solid state
resonating members for deflecting heads are elastic materials,
preferably metallic materials, particularly C-steel materials of
preferably martensitic or bainitic structure, which particularly
preferred are surface treated and/or conditioned, or titanium or
bronze alloys.
The geometric shape of solid state resonating members should allow
for an elastic oscillation thereof in resonance with the vibration
generating system, the resonating member deforming in longitudinal
direction of the vibration generating system , preferably with no
phase shift, and also oscillates along directions forming an angle
of 60.degree. to 120.degree. with the longitudinal axis of the
vibration generating system. Considering the angular displacement
between the coordinate directions or using an angled coordinate
extending from the vibration generator through the deflecting head
to the tool an in-phase motion of the output member of the
vibration generator and the tool is obtained.
The treatment tool is mounted on the deflecting head so that it
forms an angle of 60.degree. to 120.degree., particularly preferred
of 90.degree. with the longitudinal axis of the vibration
generating system. The geometry, length and mass of the treatment
tool is chosen so that it oscillates in resonance with the
deflecting head and the vibration generating system,
respectively.
Spherical, disk shaped or ring shaped deflecting resonating members
having a diameter of less than 30 mm, preferably less than 20 mm
are particularly suited for intraoral applications. In view of
improvement the efficiency hollow spherical, ring shaped or in
particular cylindrical sleeve shaped resonating members have
proven.
For connecting the deflecting head to the vibration generating
system and for connecting the treatment tool to the deflecting
head, the prior art connecting techniques as well as split
connections are suitable. Particularly, the deflecting head can be
connected to the vibration generating system and the treatment tool
can be connected to the deflecting head by soldering, welding,
adhering, screwing, bracing, wedging or by means of friction cones.
In this respect the combination of a threaded connection and a
friction cone has shown to be particularly satisfactory. Of course,
the vibration amplifier of the vibration generating system and the
deflecting head and/or the treatment tool and the deflecting head
may also be made as a one piece construction. Generally, the
connections are made in a symmetry plane of the deflecting head
defined by the axis of the vibration generator and the tool
axis.
As has been found out, liquid volumes or high pressure gas volumes
or combination of both these systems being sealing contained in
curved deflection channels surprisingly are also suited for
deflecting ultrasonics. Preferably the sealed liquid and/or gas
system is formed such that the liquid or gas volume is driven into
oscillation, particularly resonance oscillation with the latter by
excitation parallel to the longitudinal axis of the vibration
generating system. The oscillation of the liquid or gas volume thus
produced will then be transferred to a treatment tool, which by
adjusting its length, geometry and mass is tuned to resonance
frequency, preferably without inducing phase shifts (curved
coordinate extending along the axis of the deflecting channel).
Volumes of a liquid and/or high pressure gases are particularly
useful, which are sealingly confined between an entrance opening
and an outlet opening of the curved deflecting channel of a sealed
housing, sealing being obtained by means of a diaphragm or by means
of a movable plunger. The housing is shaped specific to the
respective application, the walls of the housing not being driven
into oscillation, particularly not into resonance oscillation by
the osciallation of the column of liquid.
Up to the mark are media, which when exposed to ultrasonics are
liquids, particularly low viscous liquids, as e.g. aqueous or
alcoholic solutions, oils, particularly silicone oils and synthetic
oils, polymers, quicksilver, low melting nickel alloys or highly
compressed volumes of gases, particularly inert gas volumes of
preferably more than 10 bar pressure, particularly preferred
pressures being such of more than 50 bar. In the case of liquids
which incorporate gases like water, the liquid is degassed before
being sealed into the deflecting channel.
For intraoral applications fluid tight stainless metallic housings
of the deflecting head and volumes of liquid of about 0.1 ml to 30
ml, particularly 0.5 ml to 5 ml have proven, which are sealed by
respective elastic diaphragms, especially metallic diaphragms,
preferably made from surface hardened spring steel. The two elastic
diaphragms communicate via the filling volume of the liquid and/or
the gases.
For connecting the diaphragms to the vibration generating system
and the treatment tool, respectively, all of the above described
connecting and jointing methods can be used, the diaphragms
eventually being formed with a flange on that face thereof being
remote from the filling volume. It is also a success to connect the
diaphragms in centric manner (with regard to the longitudinal axis
of the vibration generating system and the treatment tool,
respectively) to the respective end faces of the vibration
generating system and the treatment tool, respectively. Of course,
at least part of the end face of the vibration generating system
and/or the treatment tool can also be used as a diaphragm.
Particularly well suited are diaphragms which are arranged
perpendicular to the longitudinal axis of the vibration generating
system and the treatment tool, respectively. For improving the
vibration characteristics of the deflecting head diaphragms are
particularly suitable, the thickness of which continuously
decreases from the periphery thereof (fixing to the housing of the
deflecting head) towards the center thereof. For simple adjustment
of the resonance condition it is particularly useful to use
qualitatively identical diaphragms for the input diaphragm and the
output diaphragm.
For optimum oscillation of the communicating diaphragms and the
column of liquid, respectively, the diameter of the diaphragm
should at least slightly exceed the cross section of the
respectively coupling end faces of the vibration generating system
and the treatment tool, respectively, the ratio of the diameters of
input diaphragm and output diaphragm directly influencing the ratio
of amplitudes of the input and output oscillations. In view of
amplifying the amplitude of the treatment tool a diameter ratio of
input diaphragm and output diaphragm of about 2:1, particularly
about 1.5:1 has been well proven.
Such deflecting heads can be built so as to require comparatively
little space, and they are easy to clean and sterilize,
respectively. In addition the overall metal volume to be
elastically deformed is entirely limited to the two diaphragms, by
which fact the generation of heat is reduced and the efficiency is
increased as compared to solid state-deflecting heads.
Of course the deflecting head can also comprise different
communicating liquid or gas volumes or a combination of a solid
state-deflecting head and a sealed liquid or gas volume.
Particularly, such deflecting heads can comprise low melting alloys
having a hard coating, e.g. made from metal, particularly hard
metal. Such alloys are solid at ambient temperature, while the
influence of ultrasonics will at least partly change their phase
state in the sense of rendering them liquid so as to increase the
yield of a "solid state" deflecting head.
Suitable treatment tools are in particular metallic tools, e.g.
cylindrical, tubular, flame shaped, spherical, bud shaped or
conical tools as they are also used in dentistry, preferred tools
being, however, free from surface bound grain. The preparation of a
cavity is effected by at least partial sinking in of the tool
and/or by relative movement between the tool and the surface to be
treated. One can also use defined shaping tools which are sinked
into the surface to be machined in a direction, which is at least
partially parallel to the longitudinal axis of the shaping
tool.
Cleaning of teeth is carried out using tools, which have a shape
similar to the shape of a golf or hockey bat or which include an
extended shovel like work portion and are curved in accordance with
the curvature of the tooth.
For coupling energy to the surfaces to be treated, the oscillating
tool is continuously flowed around with a liquid or thixotropic
gel-type treatment medium, e.g. water or aqueous solutions of
chemical agents such that a continous liquid layer is between the
tool and the treated surface.
The rapid up and down movement of the oscillating treatment tool
will cause cavitation effects in the immediate neighbourhood of the
tool, particularly of the end face of the tool, which will result
in implosion of cavity bubbles in the liquid filled working gap
thus causing chipping surface reshaping of non-metallic materials
in the sense of an erosion process. On the other hand the
oscillation microchipping treatment of the hard dental materials
permits essentially painfree treatment without the need of
anesthesy.
The chipping rate becomes smaller with increasing working distance
and comes to a standstill upon rupture of the film of liquid. A
working distance, which is too small, in combination with the
oscillation treatment tool being urged towards the surfaces to be
treated under high pressure reduces the production of cavitation
effects and will lead to a standstill of the process.
On the other hand applying different manual pressures onto the
working tool for urging the latter towards the surface to be
treated, the working distance and thus the extent of energy
coupling will be varied. This allows for the first time for
chipping treatment of a treated surface and gentle finishing or
polishing thereof without the need of having to change the tool or
provide modifications of the treatment apparatus.
In addition it has been proven to be good to include in the
treatment medium fine abrasive hard grain (shortly referred to
below by the term abrasive particles) in view of increasing the
removal rate. Such abrasive particles are e.g. metal oxide
particles, particularly alumina particles, magnesia particles,
silicon nitride particles, boron carbide particles, glass particles
or fine diamond grain. The grain size of the particles should be
about the same order of magnitude as the double of the amplitude of
the ultrasonic vibration of the tool, i.e. the total stroke of the
ultrasonic vibration of the treatment tool particularly in view of
optimum acceleration in the working gap and optimum removal rate
resulting therefrom. It has been well proven to use suspensions of
abrasive particles the composition of which is characterized by one
unit volume of abrasive particles per 30 to 50, preferably 5 to 20
and particularly preferred 10 unit volumes of liquid. The grains
are kept suspended, e.g. by continuous stirring or flowing gas
through the suspension, e.g. in an exchangeable supply vessel.
As has been found suprisingly the dentin channels opened in the
preparation of tooth bone can be sealed during the removal process
in the sense of a wound dressing by incorporating fine grain
particles (referred to below also by the term sealing particles)
into the suspension. Particularly useful to this end is the
addition of fine unround metal oxide particles having sharp edges
(shortly referred to below by the term ingot shaped), particularly
fine alumina particles having an average diameter of less than 3
.mu.m, particularly of about 1 .mu.m. Proven mixing ratios are one
unit volume of fine grain particles per 2 to 20, perferably about
10 unit volumes of abrasive particles.
Sealing of the dentin channels opened during the preparation, which
in accordance with the invention is obtained by fine grain
particles, leads to a significant reduction in the permeability of
dentin and thus makes unnecessary an expensive wound dressing or a
pulp protection.
On the other hand the wedging of the particularly ingot shaped fine
grain particles in the treated dentin interface which is resistant
to tensile loads, for the first time provides a defined substrate,
which avoiding the problematic application of dentin etching
solutions and/or dentin bond increasing agents, which gives only a
low increase in the bonding quality, can be used to secure adhesion
for plastic dental filling materials, particularly polymer
composites or glass ionomer cements.
Surprisingly, granulates, which at least partly contain silicates
or are silanized or at least partially contain polymers, can make a
direct chemical compound with polymerizable dental filling
material, eventual displacement of the granulates in the dentin
interfaces counteracting the polymerization contraction of the
dental filling materials. Furthermore granulates, which at least
partly contain silicates, can jelly e.g. with filling cements
containing polyacrylic acid.
Supply of the suspension formed by the abrasive particles, the fine
grain particles and water (slurry) is effected e.g. by means of
nozzles provided at the handpiece or the treatment tool,
particularly through an annular nozzle member circularly extending
around the treatment tool or through an essentially tubular
treatment tool. On the other hand in the case of an exterior supply
of slurry the efficiency of removal as well as the visual control
can be improved by sucking off medium by means of a tubular
treatment tool, particularly in the case of deep cavities.
Alternatively or in addition to aqueous suspensions generally
gel-like grain slurries of the above abrasive particles and/or fine
grain particles can be used, e.g. suspensions in gels of glycerine
or gelatine or 1 to 10% chloro-hexidine-digluconate-gel can be
used. The viscosity of such gels can be varied in a way specific to
the particular specification, e.g. by addition of aerosiles, makes
possible selective application, particularly overcoming gravity,
and makes possible to renounce continuous supply of an aqueous
abrasive solution and evacuation thereof, respectively. Under the
influence of ultrasonics due to the thixotropic character of the
gel selective reduction of the viscosity in the immediate vicinity
of oscillating tool is obtained, which results in efficient
cavitation effects and a sufficient acceleration of the abrasive
particles in the working gap.
The use of such gels has been especially proven in regions which
are difficult to access, e.g. gum pockets, dental interstices or
endodontic cavities. Such gels are also very useful for making
tooth restorations and represent an alternative to a continuous
supply of an abrasive medium. Of course, the liquids or gels may
additionally include chemically active ingredients, e.g. Calcium
chelate forming agents (EDTA solution) to chemically assist the
removal of hard tissue or sodium hypochlorite solution for
disolving remnants of soft tissue, e.g. during the preparation of
endodontic cavities, or organic acid solutions for simultaneous
removal of smear layers induced by the treatment and/or for
micromorphological restructuration of the treated surfaces or
active substances for reducing the number of germs at the treated
surfaces and in the surroundings thereof (e.g. reduction of germs
in gum pockets), respectively.
So it proved to be good in the selective removal of carious dental
hard substances to renounce addition of coarse abrasive particles
and to use instead liquids or gels additionally containing e.g.
sodium hypochlorite solution.
Of course, liquids of high viscosity e.g. polymer composites can be
thixotropically made liquid under the influence of ultrasonics and
can be pressed into a thin film between dental cavities and dental
restoration parts while being exposed to ultrasonics so as to form
the fixing composite.
The defects of hard tissue resulting from cutting removal of
carious dental hard substances in dentistry are prepared in the
sense of cavities and tooth stumps, respectively in compliance with
exact preparing guidelines (expert's knowledge) for improving the
stability or the edge position of restoring members to be
inserted.
Intraoral cavities, e.g. for receiving insertion fillings or
partial crowns can each be subdivided into one or plurality of
occlusal cavity segments complying with the expert's knowledge
and/or one or a plurality of approximal or buccal or oral cavity
segments each having diverging opposing walls.
In accordance with the invention this knowledge of the expert is
incorporated into a set of standardized treatment tools of
different size gradation, each such treatment tool being formed as
the negative model of the cavity segment to be prepared. In
particular production of at least one shaping tool for treatment of
occlusal cavity segments and/or at least one shaping tool for
shaping approximal, buccal or oral cavity segments in at least one
size, preferable in different size gradations has proven to be
good. The preparation of the cavity is carried out after the
individual removal of e.g. carious dental hard substance has been
effected, and this preparation is made by sinking in one or a
plurality of oscillating shaping tools in accordance with the
invention to the preferably pretreated surfaces in a direction
being parallel to the longitudinal axis. Combined geometries of a
cavity result from adjacent sinking in of different segment tools,
particularly after preselection among suitable sizes of shaping
tools.
The restoration of such cavities, in accordance with the present
invention is carried out by inserting of at least one standardized
mating member or filling member having the same geometry as the
treatment tool(s) used, which mating or filling member is selected
from a set of shaped members corresponding with the respective
geometries of the shaping tools as to the shapes and size
gradation. More particularly, the use of adhesive restoration
methods using polymer composites as well as conditioning of the
surfaces of the cavity walls and of surfaces of the filling members
or surfaces of the cavity or surfaces of adjacent filling member
segments in a way being specific for the material, has been proven
to be good. Thus preparation of the cavity and final restoration is
carried out in the same treatment session avoiding complicated
modelling techniques as well as the expensive production of
individual mating members in a laboratory.
Still furthermore shaping tools in accordance with the present
invention can also be used in the preparation of surface segments,
particularly the surfaces of tooth stumps, e.g. in connection with
the preparation of veneer shells or of crown stumps. Again the
knowledge of the expert relating to the shaping of the stump
surfaces extending essentially parallel to the longitudinal axis of
the tooth is put into a set of essentially shovel shaped
preparation tools of different size gradations and different radii
of curvature. Particularly the knowledge of the expert relating to
preparation of edge transisions, particularly of the edges of
crowns, e.g. in the form of stepped transitions or flute
transitions each with or without edge chamfer can be put into a
shaping treatment tool, which at least partially is formed as the
negative of the surface geometry to be produced. The preparation of
edge transisions preferably is made by circular guiding of such
tools parallel to the longitudinal axis of the shaping tool along
the entire edge transition to be reshaped or to be finished. This
method has proven to be particularly useful, since eventual
imprecision in the production of models can be integrated as to the
geometry by integrating into the geometry the geometry of adjacent
precisely modelled surface sections of the model stump additionally
considering the expert's knowledge, which integration is preferably
carried out by reworking of the model stump using identical shaping
treatment tools.
The use of a set of tools designed in analogy to the surfaces of
the dental roots or surface segments thereof, which e.g. may have
the shape of a scoop or a golf or hockey bat, also allows to remove
tooth plaque and adsorbed hard substances, e.g. dental tarter from
supragingival and subgingival root surfaces, the composition of the
working medium used (e.g. water or an abrasive suspension) as well
as the vibration mode of the tools allowing for an essentially
selective removal of dental tarter and eventually of concrements
without the danger of major volumes of healthy dental hard tissue
being removed or being modified e.g. in the sense of a surface
roughening.
Futhermore use of at least partially oval treatment tools for the
first time allows to prepare endodontic cavities according to their
form, which in analogy to the cross section of the root normally is
oval, using an instrument.
Surprisingly, it was further found, that essentially wire shaped,
cylindrical or cutting edge shaped treatment tools e.g. made from
chrome and nickel containing metal alloys when exposed to
ultrasonics and not cooled by water are selectively heated by
internal friction effects and can be used for cutting treatment of
soft tissues and for coagulation of blood vessels, which have been
opened. Such treatment tools are particularly useful, which favour
the production of frictional heat when exposed to ultrasonics e.g.
due to the fact that they comprise at least two different materials
or due to induction of relative movements of the treatment tool
with respect to the deflecting head. Using such tools cuts in soft
tissue can be made in analogy to CO.sub.2 lasers or high frequency
electric tools, without occurence of injuries due to undesired
optical reflection phenomena or electric sparks.
Heat producing tools can especially be used in endodontics as
filing members after having carried out the preparation of a root
channel, preferably using treatment tools of same shape. The
production of heat allows to use e.g. thermoplastic root filling
materials, which are at least partially transferred into the liquid
state by the oscillating heat producing tool and which due to
forward feeding of the tool in the root channel are pressed into a
small volume and which after cooling, which is caused by switching
of the ultrasonic oscillation, preferably being adsorbed on the
surfaces of the dental hard tissues and the treatment tool fulfill
the function of a bonding material (sealer), which closes the
individual cavities defined between the dentin walls of the root
channel and the treatment tool, which simultaneously serves as a
macro-filling member. Cooling of the tool, which due to the conical
shape thereof is a directed cooling which is from the tip of the
tool to the basis thereof, allows for gap free sealing of the
cavities defined between the tool and the wall of the root channel.
At the same time the tool after having been detached from the
deflecting head is preferably left in the root channel as a
geometrically defined shaped member in the sense of a filling
member. Preferably the tool is reduced in length corresponding to
the individual longitudinal extension of the dental root.
Of course, use of the treatment apparatus in accordance with the
present invention and of the methods in accordance with the present
invention is not limited to applications in the field of dentistry;
they can also be used in equivalent medical and non-medical
applications including industrial applications.
The invention will now be explained in more detail referring to
preferred embodiments and to the enclosed drawings. Therein
FIG. 1: is an axial section through the end portion of a dental
angled hand piece for treatment of dental material;
FIG. 2: is an enlarged section through a sound deflecting unit of
the hand piece shown in FIG. 1;
FIG. 3: is a schematic representation of the hand piece of FIG. 1
under operational conditions;
FIG. 4: shows a first step in the preparation of an extended
carious region of a tooth using a hand piece in accordance with
FIG. 1, seen in*lateral direction, wherein a laterally open recess
of the tooth is produced;
FIG. 5: is a section taken along line V--V of FIG. 4;
FIG. 6: is a second step of the preparation following the step
shown in FIG. 4, wherein a central recess has been produced in the
tooth, as seen in lateral direction;
FIG. 7: is a section along cutting line VII--VII of FIG. 6;
FIG. 8: is a further step in the preparation and restoration in the
tooth following the steps shown in FIGS. 4 to 6 and a further step
not shown in the drawings and wherein a filling member made from
dental replacement material is inserted into the previously created
central recess of the tooth, seen in lateral direction;
FIG. 9: shows a section along line IX--IX of FIG. 8;
FIG. 10 is a lateral view of a step as it is carried out for
preparing a tooth stump before mounting a crown;
FIG. 11: is a cut along line XI--XI of FIG. 10;
FIG. 12: is a lateral view of a treatment step for treating the
upper end portions of the exterior surface of a dental root with an
ultrasonic tool;
FIG. 13: shows further dental works using ultrasonic tools, wherein
flesh is cut (left portion of the figure) or bone material is
removed (right hand portion of the figure);
FIG. 14: is a lateral view of a step of a root channel treatment,
which is carried out using an ultrasonic tool;
FIG. 15: is a section along line XV--XV of FIG. 14;
FIG. 16: is a similar representation as FIG. 3, wherein, however, a
modified hand piece comprising a solid state sound deflecting unit
is shown;
FIG. 17: is a separate representation of the sound deflecting unit
of FIG. 16, which will be used for explaining its function in more
detail; and
FIG. 18: is a lateral view of a preparation of a cavity using an
ultrasonic shaping tool, which at the same time serves as a shaped
or filling member.
FIG. 1 shows the end portion of a dental angled hand piece
generally shown at 10. The hand piece 10 has a tubular housing 12
which also has the function of a grip and in which by means of
suspension elements 14 an ultrasonic vibration generator generally
shown at 16 is mounted.
The ultrasonic vibration generator 16 comprises a piezoelectric
ultrasonic transducer 18, which in turn may comprise a plurality of
axially staggered disks made from piezoelectric ceramic material,
which disks are mechanically series connected. Mass members 22, 24
of rotational symmetry are arranged on the end faces of the
ultrasonic transducer 18, e.g. by being srewed thereon or adhered
thereto.
At the end of the mass member 24, which in the drawings is at the
right hand end, an amplifying member 26 is provided, which
concentrates ultrasonic energy received by its left hand end face
towards the free end thereof due to the progressive reduction of
its cross section thus providing an ampliofication of the
amplitude. Such amplifying members are often termed as
sonotrodes.
The right hand end of the housing 12 carries a deflecting head
generally shown at 28. The deflecting head comprises a deflector
housing 30, the exterior shape of which is similar to a ridge
prism. A deflecting channel 32 is formed in the deflector housing
30, the central axis of which extends along a quarter of a circle.
The transversal cross section of the deflector channel is circular,
the cross sectional area continuously diminishing from the inlet
opening of the deflector channel 32, which in the drawings is the
left hand opening and which is positioned in the vertical plane,
towards a lower outlet opening of the deflector channel 32, which
in the drawings is oriented in horizontal direction.
The ends of the deflecting passageway 32 are sealed by metal
diaphragms 33, 34, which e.g. can be thin steel diaphragms.
A volume 35 of liquid, which is a good sound conductor, is
contained in the deflecting passageway 32 in fluid tight manner.
Preferably this liquid is a metal, which at ambient temperature or
a temperature being slightly above room temperature
(40-100.degree.) is in the liquid state, e.g. quicksilver or a low
melting nickel alloy or comprises inherently solid or semi-solid or
gel-type media, which become liquid when exposed to ultrasonics.
Alternatively degassed nonmetal liquids can be used, e.g. degassed
water or degassed silicone oil. Still alternatively highly
compressed gases may be contained in the deflector channel 32 in
fluid tight manner, the pressure of which may be e.g. about 50
atm.
The left hand diaphragm 33 as seen in the drawings is connected to
the free end of the amplifying member 28, the metallic diaphragm 34
carrying a dental tool 36, which in accordance with FIGS. 1 and 2
has rod shaped geometry.
In view of exchanging the tool 36, a mounting member 38 may
provided on the metallic diaphragm 34 in accordance with FIG. 2,
into which the tool 36 is screwed.
In FIG. 3 H designates the axis of handpiece 44, which is also the
axis of the vibration generator 16. W designates the axis of the
tool 36. These two axis extend in perpendicular directions and due
to this fact the hand piece 44 allows for the same ergonomic
operating conditions as a conventional mechanical angled hand
piece. The deflecting head 28 provides for deflection of the
ultrasonic vibrations produced by the vibration generator 16
towards the tool 36.
The hand piece described above operates as follows:
Ultrasonic energy, which is generated by the vibratory system
comprising the ultrasonic transducer 18 and the mass members 22, 24
is transferred to the metallic diaphragm 33 via the amplifying
member 26 so that its amplitude is increased. The respective
essentially sinusoidal movement of the metallic diaphragm 33
schematically shown in FIG. 4 at 40 and having the amplitude "a"
induces respective pressure waves in the volume of liquid 35. The
metallic membrance 34 is driven by these pressure waves
correspondingly, the amplitude being again increased in accordance
with reduction of the cross section of the deflector channel 32.
The essentially sinusoidal movement of the metallic diaphragm 34 is
shown at 42 (amplitude "A"). This movement is transferred to the
tool 36 and can serve for removal of material, as will described in
more detail below refering to FIG. 3.
It is to be noted, that the vibration amplitudes shown at 40 and 42
are not shown up to scale with respect to the dimensions of the
deflecting head 28. Actually, the vibration amplitudes "A" of the
tool are in the region of about 2 to 50 .mu.m.
As may be seen from FIG. 3 an angled hand piece 44, which is used
for removal of dental material has the same structure as the hand
piece 10 shown in FIG. 1 as far as the generation of ultrasonics
and deflection of the ultrasonics is concerned. Thus respective
components have the same reference numerals affixed thereto. In
addition a discharge tube 46 is provided at the end of the housing,
for dispensing an abrasive treatment medium 48. The discharge tube
46 is connected to the feed side of a pump 50, which draws the
abrasive treatment medium from a mixing vessel 52.
In a modified embodiment an anular discharge nozzle ramp
surrounding the tool 36 may be used instead of the discharge tube
46 or together with the latter, which via a plurality of nozzles
oriented towards the forward end portion of the tool 36 discharges
abrasive treatment medium, preferably to the vicinity of the upper
end of the tool.
A supply 54 of mixture contained in the mixinig vessel 52 consists
of water, in which large abrasive particles 56, medium size
abrasive particles 58 and fine abrasive sealing particles 60 are
distributed. These different particles are schematically identified
by points, small circles and small triangles, respectively.
The large abrasive particles 56 have a diameter essentially
corresponding to the total stroke of the ultrasonic vibrations of
the tool 36, which thus amounts to about 2A. Actually the diameters
for the large abrasive particles are thus smaller than 100 m.mu..
The large abrasive particles 56 have a surface including a large
number of edges, which is obtained by crushing of grinding of hard
material. Thus these particles have goods cutting characteristics.
The material of the large abrasive hard grains is selected in view
of the respective application. In order to achieve high removal
rates silicon carbide materials have proven to be good, good
results being obtained with particle sizes between 50 and 80
.mu.m.
The smaller abrasive particles 60 are useful in slower removal and
thus in finishing the surface treated. Their diameter can be
roughly chosen to be about half or one third of the diameter of the
large abrasive particles 56. Also one can choose for these abrasive
particles materials, which tend less to formation of strong cutting
edges than silicon carbide materials. Examples for such materials
are e.g. alumina ceramic materials. In practical work e.g. alumina
ceramic particles having the shape of small plates or small disks
and having a diameter of about 25 .mu.m have proven to be good,
these particles also excelling by hydrophilic properties of their
surface. Hydrophilic surfaces of particles are advantageous in view
of making stable slurries in water which can be well handled.
The sealing particles 60 are of small diameter. Their diameter is
chosen in view of the diameter of small dentin channels of the
dental material which are to be closed by the sealing particles 60
as will be described in more detail below. In practical
applications the diameter of these sealing particles is below 3
.mu.m, preferable at about 1 .mu.m. Suitable materials for the
sealing particles 60 are especially again alumina ceramic
materials. In the production of the sealing particles care is taken
to obtain a surface having sharp edges. One reason for this is to
give these particles still useful abrasive properties in spite of
their small diameter, since these particles should also contribute
to removal of material; another reason for this is to obtain
optimum reliable mechanical engagement of the sealing particles to
the ends of the small dentin channels and to surface roughnesses of
the surface of the treated cavity. Thus the sealing particles form
adhering points to which the filling material may cling and
effectively adhere.
As to the mixing ratios of the large abrasive particles 56, the
smaller abrasive particles 58 and the sealing particles 60
reference to the explanations given in the introductory part of the
specification is made.
The above information relating to the particle sizes relates to the
desired sizes of particles in applications, where removal of
material is desired. If the particles are made from brittle
material, which disintegrates when exposed to ultrasonics, the size
of the particles found in the discharged treatment medium may be
larger, provided disintegration of these particles at the working
site will result in the desired particles sizes.
In view of obtaining a high removal rate it is desirable that the
large abrasive particles 56, the medium size abrasive particles 58
and the fine abrasive sealing particles 60 each show only a small
standard deviation of the grain size from a desired average
diameter.
A mixing rod 62 made from magnetic material is rotated in the
mixing vessel 52 by means of a rotating field produced by a
solenoid coil 64.
In the lower right hand portion of FIG. 3 the coronal portion 64 of
a tooth 66 and its enamel layer 68, its dentin volume 70 and its
tooth cavity 72 is shown. Small diameter dentin channels 74 extend
from the tooth cavity 72 through the dentin volume 70 up to the
enamel layer 68.
A recess 76 has been produced in the tooth 66 starting from the
occlusal surface 66 and extending into the dentin volume 70
penetrating the enamel layer 68. Removal of the respective amount
of material has been effected by urging the lower end face and the
lateral surfaces of the tool 36 towards the dental enamel material
and the dentin material, respectively, while simultaneously
discharging abrasive treatment medium 48 from the discharge tube 46
and simultaneously supplying ultrasonics to the tool 36. In doing
so the vibrating surface of the tool imparts to the abrasive
particles a high velocity and when these particles impinge onto the
opposing surface of the material they will detach therefrom small
fragments. This kind of material removal is gentle and does not
result in major damaging of tissues, particularly fractures. By
corresponding control of the tool in the three coordinate
directions and by rotating the hand piece about the axis
corresponding to the coordinate directions (these movements are
symbolically shown at 98), the dentist can produce the respectively
required tooth cavity.
FIG. 3 shows the situation found after preparation of the cavity
has been completed. One recognizes that the ends of the small
dentin channels 74, which have been opened by preparing the cavity,
have been closed by some of the small sealing particles 60. By this
fact the permeability of the dentin volume being adjacent to the
cavity is reduced in the sense of an isolating layer functioning as
a pulp protection.
The catering of a larger carious dental defect will now be
described referring to FIGS. 4 to 9.
In a first step shown in FIGS. 4 and 5 a lateral carious region of
the tooth is removed using a first shaping tool 80 which is fixed
to the deflecting head 28. The cross sectional view of this tool
has the form a curved trapezoid, while the axial section of the
tool has the shape of a wedge. By mere axial feeding of the shaping
tool 80, which receives ultrasonics via the deflecting head 28,
while simultaneously supplying abrasive treatment medium 48, the
carious rim portion of the tooth has been removed. In doing so a
recess 82 has been formed in the tooth 66, the shape of which is
complementary to the exterior shape of the shaping tool 80. At the
same time the edges of the cavity can be definitely shaped, e.g. by
forming a partial edge chamfer.
In a second step, which is shown in FIGS. 6 and 7, a central recess
84 is formed in the tooth 66, the edge contour of which has about
the shape of the cipher "8" oriented in horizontal direction. To
this end a further shaping tool 86 is fed in axial direction, which
is of corresponding cross section. Again abrasive treatment medium
48 is supplied, which will enter between the exterior surface of
the shaping tool 86 and the dental material.
It may be seen from FIG. 8 that subsequent to the forming of the
two recesses 82 and 84 a first shaped filling member 88 has been
inserted into the recess 82, which consists of dental replacement
material and the circumferential shape of which corresponds to that
one of the shaping tool 80. The shaped member 88 is connected to
the dental material by means of a joint composite layer 90. The
upper end face of the shaped filling member 88 has been machined
using a treatment tool, which actually can be similar to the one
shown in FIG. 1, such that it is an image of the original occlusal
surface.
A further shaped filling member 92 is just being inserted into the
central recess 84. The exterior contour thereof corresponds to the
exterior contour of the shaped tool 86. Between the exterior
surface of the shaped filling member 92 and the wall surfaces of
the recess 84 a further joint composite layer 94 is shown, which
has not yet cured. Ultrasonics is now supplied to the upper end of
the shaped filling member 92 using a pressing tool 96, which now is
mounted on the deflecting head 28 of the hand piece 10. Thus
insertion of the shaped filling member 92 into the recess 84 is
assisted, since the viscosity of the joint composite material is
reduced by the vibration. This way of inserting the shaped filling
member is advantageous in view of joint composite layers or
adhesive layers, the thickness of which is as small as
possible.
FIG. 8 shows the standard shaped filling member 92, which has been
taken from a supply of the dentist to be used in recesses created
using the shaped tool 86, the shaped filling member having is
original geometry. After curing of the joint composite layer 94
those portions of the shaped filling member 92 projecting beyond
the occlusal surface must be removed so that the end face of the
shaped filling member 92 being formed again images the original
occlusal surface. The respective contours have been indicated in
FIG. 9 by narrow lines.
In the description of the restoring phase of catering described
above referring to FIG. 8, for the sake of better explanation of
the invention it was submitted that the first shaped filling member
88 is first inserted and is fixed in place by composite material,
its upper end face then being machined in accordance with the
desired geometry of the occlusal surface, the shaped filling member
92 then being inserted into the cavity. It is to be understood,
that in such proceeding the composite layer being between the two
shaped filling members is applied only when the shaped filling
member 92 is inserted so that the two shaped filling members are
well interconnected.
In practical work one will generally proceed such that the two
shaped filling members 88 and 92 are inserted into the cavity in a
common step using composite material and that machining of the
upper end faces of the two shaped filling members for providing the
desired geometry of the occlusal surface is also carried out in a
common step.
FIGS. 10 and 11 show the use of ultrasonic tools in the preparation
of tooth stumps for subsequent application of a crown (right hand
side: flute preparation; left hand side: preparation of a chamfered
shoulder). This machining is again carried out under simultaneous
supply of an abrasive treatment medium 48.
The left hand portions of FIGS. 10 and 11 show a tool 98, the
vertical cross section of which has the shape of an rectangle, the
transversal section of which has the shape of a curved flat
rectangle having rounded edges. The curvature of the cross section
is chosen in view of the tooth curvature prevailing in the region
to be treated. For practical work the dentist disposes of a
plurality of such treatment tools of different curvature, which may
be chosen from a set of tools.
As may be seen from FIG. 10, the lower end face 100 of the tool 98
is downwardly sloped so that this tool will produce a vertical
lateral surface 102 on the tooth stump, which at the lower end is
limited by a downwardly and outwardly sloped flute 104.
It is to be noted that the geometry of the shape produced can show
different combinations as to the horizontal diameter and the
vertical diameter: the flute can be produced with the smaller
diameter and the downwardly sloped shoulder can be produced with
the larger diameter.
The tool 106 shown in the right hand portion of FIGS. 10 and 11 is
similar to the tool 98, however, it has only a smaller
circumferential extension so that it can be generally used for
treatment of tooth stumps of extremely different circumferential
curvature. The lower end face 108 of the tool 106 is e.g. stepped:
it comprises a portion of the end face being perpendicular to the
axis of the tool and a succeeding downwardly sloped portion of the
end face. Thus the tool 106 will produce on the tooth stump again a
vertical lateral face 110 and an outwardly and downwardly sloping
chamfer 112, a horizontal shoulder 114 being produced in addition,
which is located between the chamfer 112 and the lateral surface
110.
FIG. 12 illustrates the gentle removal of material, particularly
supragingival and subgingival dental tarter, root concrements
and/or plaque at the cervical end of dental roots 116, 118. A first
tool 120 has a shaft 122, which may be of similar appearance as the
shaft of the tool 106, and an extended work portion 124 is arranged
at the lower end of the shaft 122, which generally has the shape of
a planting shovel thus being curved in circumferential direction in
accordance with the curvature of the dental root 116. The tool 120
has been inserted into a gum pocket 126, which using a syringe 128
has been filled with treatment medium 130. The latter comprises a
liquid base material of higher viscosity, wherein again abrasive
particles 132 have been distributed and which additionally may
comprise, if desired, chemical etching agents and/or germicidal
substances.
In a modified process one may also use a treatment medium 130 not
containing abrasive particles.
Furthermore it should be noted that the tools 120 and 134 need not
have a geometrically defined cutting edge and in so far differ from
conventinal curets.
The right hand portion of FIG. 12 shows a tool 134 used for removal
of dental tarter for treatment of the exterior surface of the
dental root 118. This tool has the shape of golf bat or hockey bat.
The tool 134 thus includes a shaft 136 carrying a narrow working
portion 138 extending in transversal direction. The tool 134 is
well suited for treatment of longitudinally curved dental roots or
of dental roots having surfaces being concavely curved in
circumferential direction.
The left hand portion of FIG. 13 shows a tool 140 (ultrasonic
scalpel) which is used for removal of soft tissue, particularly
tooth gum or for preparation of soft tissue incisions. A shaft 142
carries a transversal work portion 144 made from a material which
will transform ultrasonic energy into heat. A suitable such
material is e.g. a compound material comprising two or more
different layers of material. Respective examples are bimetallic
strips of material or metals having a ceramic coating. Examples for
materials showing high interior volume friction are stainless
steels. The tool 140 thus works as a ultrasonic cauter and can
produce in the tooth gum shown at 146 incisions in precisely
controllable manner, cut off parts of the tissue or cauterize
vessels.
The right hand portion of FIG. 13 shows a bone preparation tool 148
for removal of bone material 150. A rod shaped shaft 152 carries an
e.g. spherical work portion 154. In a modified tool the work
portion 154 may have the form of a V-shaped or pyramidal chisel
tip. Preferably the tool 148 shown in the right hand portion of
FIG. 13 is again used simultaneously supplying an abrasive
treatment medium 48.
FIG. 14 shows a tool 156 useful in the preparation of a dental
tooth channel 158. The latter has already been opened in the
conventional way or using a tool described above with reference to
FIGS. 1 through 7 and has
been widened mainly using conventional tools. The tool 156 is used
for gentle final treatment of the dental root channel 158. To this
end it has been given a transversal cross section corresponding to
the shape of a rectangle having rounded edges or to the shape of an
oval, the transversal cross section diminishing towards the free
end of the tool 156. Seen in longitudinal direction the tool 156
has the shape of a slightly curved wedge.
The tool 156 has been selected from a set of tools, wherein the
invididual geometry of the tools reflects the average standard
geometries (shape, size, diameter) of dental root channels of the
different teeth and groups of teeth, respectively.
In a modification of the embodiment shown in FIG. 14, the tool 156
used for preparing a dental root channel can also be provided with
a rated break point or separating point marker so that that portion
of the tool being complementary to the treated dental root channel
can be anchored in the treated root channel to form a restoring
member after breaking of the rated break point or severing at the
separation marker. This portion of the tool 156 which has the form
of a pin like shaped filling member can then be used as an
anchoring member for built-up members. Suitable materials for such
tools are ceramic materials, metals used for making dental
prosthesis or implants as well as plastics materials.
The right hand portions of FIGS. 14 and 15 show a dental root
channel 160 which has not been prepared.
FIG. 16 shows an ultrasonic teeth preparation apparatus which is
very similar to the one shown in FIG. 3. Functionally equivalent
components have again the same reference numerals affixed
thereto.
The deflecting head 28 now comprises a ring member 162, which has
been designed as to its material and as to its geometry such that
is has four maxima of vibration which are spaced by 90.degree. in
circumferential direction and lie in portions 162a-162d of the ring
member as indicated in FIG. 17. The end of the amplifying member 26
is coupled to that one of the maxima of vibration being located in
the portion 162a of the ring member; that one of the vibration
maxima which is spaced in downward direction by 90.degree. with
respect to the axis of the vibration generator 16 and lies in
portion 162d of the ring member is connected to the tool 36. The
ring member 162 thus provides for an angular deflection of the
ultrasonic energy without amplification of the amplitude. In a
direction being perpendicular to the drawing plane, i.e. in axial
direction, the ring member 162 is sufficiently dimensioned to
warrant that its modes of vibration are pure breathing movements
and do not or only to an negligible amount comprise torsional
components in circumferential direction.
If the ring member 162 is designed so as to have three maxima of
vibration, one can obtain an angle included between the axis H of
the hand piece and the axis W of the tool (deflecting angle)
corresponding to 120.degree.. With n maxima of vibration one can
realize deflecting angles of 360.degree./n as well as integral
multiples thereof.
If intermediate angles are desired, these can be obtained by
varying the thickness or the axial extension of the wall of the
ring member in circumferential direction, since in such case the
nodes of vibration are not equally distributed in circumferential
direction.
In a modification of the embodiments described above an asymmetric
design of the ring member can be adopted in such manner that the
portion of the ring member providing the driving movement shows a
greater amplitude than the one found in the driven portion of the
ring member. In such case the ring member does not any longer show
full rotational symmetry, e.g. it is formed with a
circumferentially varying thickness of its wall or its axial
extension.
In accordance with a further modification in such cases, where the
full amplitude of the vibration produced by the vibration generator
16 is not required at the tool, the tool 36 may be also connected
to a ring portion of the ring member 162 lying between a maximum of
vibration and a node of vibration.
From FIG. 17 it may also be seen that at a moment, when the
vibration generator will exert a pushing force onto the portion
162a of the ring member, a pushing force is exerted onto the tool
by the portion 162d of the ring member. Power transfer from the
vibration generator to the tool is thus obtained without a phase
shift.
In the preparation apparatus shown in FIG. 16 the tool 36 is hollow
and is connected by means of a hose 164 to the output of a second
pump 166 drawing abrasive treatment medium 170 from a supply vessel
168. The treatment medium in practical work again consists of
water, large abrasive particles 172 and in the considered
embodiment furthermore of sealing particles 174 for closing the
small dentin channels 74. The fact that the treatment medium 170
does contain no praticles corresponding to the medium size abrasive
particles 58 is meant to indicate that the treatment medium 170 may
differ from the treatment medium 48. Such difference may also
pertain to further additions to the treatment medium, which serve
for control of the viscosity or have medicinal function.
A double arrow shown in the suction line of the pump 166 indicates
that this pump can also be used for evacuating used treatment
medium through the tool 36.
FIG. 18 shows a further embodiment of the invention, wherein the
shaping tool is formed by the shaped filling member later be
connected to the dental material.
A mounting member 178 is moulded into the upper end of a shaped
filling member 176, the geometry of which essentially corresponds
to the geometry of the shaping tool 86. The mounting member 178
mates the mounting part 38. The shaped filling member 176 has an
upper portion formed with a rated break point 180. Thus after
sinking in the shaped filling member 176 (simultaneously supplying
an abrasive treatment medium as has been described above) the
mounting member 180 can be broken away or severed by a blow. The
shaped filling member 166 will then be adhesively connected to the
dental material as has been described above and the upper portion
of the shaped filling member 176 is machined for reforming the
occlusal surface.
As has been pointed out above referring to FIG. 14, already, a
further example for a shaped filling member simultaneously being
used as a shaping tool is a tool for the treatment of dental root
channels as shown in FIG. 14.
Materials suited for making tools which also represent shaped
filling members are metal alloys, e.g. titanium alloys, as well as
oxide type or non-oxide type ceramic materials, particularly
alumina ceramics or silicon-carbide sintered materials.
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